Brachial Artery Blood Flow Research Articles

Effects of Different Eccentric Cycling Intensities on Brachial Artery Endothelial Shear Stress and Blood Flow Patterns

ABSTRACT Eccentric exercise has gained attention as a novel exercise modality that increases muscle performance at a lower metabolic demand. However, vascular responses to eccentric cycling (ECC) are unknown, thus gaining knowledge regarding endothelial shear stress (ESS) during ECC may be crucial for its application in patients. The purpose of this study was to explore ECC-induced blood flow patterns and ESS across three different intensities in ECC. Eighteen young, apparently healthy subjects were recruited for two laboratory visits. Maximum oxygen consumption, power output, and blood lactate (BLa) threshold were measured to determine workload intensities. Blood flow patterns in the brachial artery were measured via ultrasound imaging and Doppler on an eccentric ergometer during a 5 min workload steady exercise test at low (BLa of 0–2 mmol/L), moderate (BLa 2–4 mmol/L), and high intensity (BLa levels > 4 mmol/L). There was a significant increase in the antegrade ESS in an intensity-dependent manner (baseline: 44.2 ± 8.97; low: 55.6 ± 15.2; moderate: 56.0 ± 10.5; high: 70.7 ± 14.9, all dynes/cm2, all p values < 0.0002) with the exception between low and moderate and Re (AU) showed turbulent flow at all intensities. Regarding retrograde flow, ESS also increased in an intensity-dependent manner (baseline 9.72 ± 4.38; low: 12.5 ± 3.93; moderate: 15.8 ± 5.45; high: 15.7 ± 6.55, all dynes/cm2, all p values < 0.015) with the exception between high and moderate and Re (AU) showed laminar flow in all intensities. ECC produced exercise-induced blood flow patterns that are intensity-dependent. This suggests that ECC could be beneficial as a modulator of endothelial homeostasis.

Induced blood flow oscillations at 0.1 Hz protects oxygenation of severely ischemic tissue in humans.

Generating 10-s (∼0.1 Hz) fluctuations or "oscillations" in arterial pressure and blood flow blunts reductions in cerebral tissue oxygenation in response to 15%-20% reductions in cerebral blood flow. To examine the effect of 0.1 Hz hemodynamic oscillations on tissue oxygenation during severe ischemia, we developed a partial limb ischemia protocol targeting a 70%-80% reduction in blood flow. We hypothesized that 0.1 Hz hemodynamic oscillations would attenuate reductions in tissue oxygenation during severe ischemia. Thirteen healthy humans (6 M and 7 F; 27.3 ± 4.2 yr) completed two experimental protocols separated by ≥48 h. In both conditions, an upper arm cuff was used to decrease brachial artery (BA) blood velocity by ∼70%-80% from baseline. In the oscillation condition (0.1 Hz), 0.1 Hz hemodynamic oscillations were induced by intermittently inflating and deflating bilateral thigh cuffs every 5 s during forearm ischemia. In the control condition (0 Hz), the thigh cuffs were inactive. BA blood flow, forearm tissue oxygenation (SmO2), and arterial pressure were measured continuously. The initial reduction in BA blood velocity was tightly matched between protocols (0 Hz: -76.9 ± 7.9% vs. 0.1 Hz: -75.5 ± 7.4%, P = 0.49). Although 0.1 Hz oscillations during forearm ischemia had no effect on the reduction in BA velocity (0 Hz: -73.0 ± 9.9% vs. 0.1 Hz: -73.3 ± 8.2%, P = 0.91), the reduction in SmO2 was attenuated (0 Hz: -35.7 ± 8.6% vs. 0.1 Hz: -27.2 ± 8.9%, P = 0.01). These data provide further evidence for the use of 0.1 Hz hemodynamic oscillations as a potential therapeutic intervention for conditions associated with severe tissue ischemia (e.g., hemorrhage and stroke).NEW & NOTEWORTHY We investigated the effects of induced 10-s (0.1 Hz) oscillations in blood flow on forearm tissue oxygenation during severe ischemia. Intermittent inflation of bilateral thigh cuffs was used as a clinically applicable method to drive blood flow oscillations. In support of our hypothesis, 0.1 Hz oscillations in blood flow blunted reductions in forearm tissue oxygenation. These results further support the potential use of oscillatory hemodynamics as a therapeutic intervention for ischemic conditions.

Peripheral chemoreflex restrains skeletal muscle blood flow during exercise in participants with treated hypertension.

We tested the hypothesis that in human hypertension, an increased tonicity/sensitivity of the peripheral chemoreflex causes a sympathetically mediated restraint of nutritive blood flow to the exercising muscles. Fourteen patients with treated hypertension (age 69±11 years, 136±12/80±11mmHg; mean±SD) were studied under conditions of intravenous 0.9% saline (control) and low-dose dopamine (2µgkg-1min-1) to inhibit the peripheral chemoreflex, at baseline, during isocapnic hypoxic rebreathing and during rhythmic handgrip exercise (3min, 50% maximum voluntary contraction). At baseline, dopamine did not change mean blood pressure (95±10 vs. 98±10mmHg, P=0.155) but increased brachial artery blood flow (59±20 vs. 48±16mlmin-1, P=0.030) and vascular conductance (0.565±0.246 vs. 0.483±0.160mlmin-1mmHg-1; P=0.039). Dopamine attenuated the increase in mean blood pressure (∆3±4 vs. ∆8 ±6mmHg, P=0.007) to isocapnic hypoxic rebreathing and reduced peripheral chemoreflex sensitivity by 28±37% (P=0.044). Rhythmic handgrip exercise induced increases in brachial artery blood flow and vascular conductance (both P<0.05 vs. rest after 45s) that were greater with dopamine than saline (e.g. Δ76±54 vs. Δ60±43mlmin-1 and Δ0.730±0.440 vs. Δ0.570±0.424mlmin-1mmHg-1, respectively, at 60s; main effect of condition both P<0.0001). Our results indicate that the peripheral chemoreflex is tonically active at rest and restrains the blood flow and vascular conductance increases to exercise in treated human hypertension. KEY POINTS: It was hypothesised that in human hypertension, an increased tonicity/sensitivity of the peripheral chemoreflex causes a sympathetically mediated restraint of nutritive blood flow to the exercising muscles. Treated patients with hypertension (n=14) were studied under conditions of intravenous 0.9% saline (control) and low-dose dopamine (2 µgkg-1min-1) to inhibit the peripheral chemoreflex. Low-dose dopamine reduced resting ventilation and peripheral chemoreflex sensitivity, and while mean blood pressure was unchanged, brachial artery blood flow and vascular conductance were increased. Low-dose dopamine augmented the brachial artery blood flow and vascular conductance responses to rhythmic handgrip. These findings indicate that the peripheral chemoreflex is tonically active at rest and restrains the blood flow, and vascular conductance increases to exercise in treated human hypertension.

Impact of moderate-intensity aerobic exercise in combined hypoxic and hot conditions on endothelial function.

There is no study that has investigated the impact of exercise in a combined hypoxic and hot environment on endothelial function. Therefore, we tested whether aerobic exercise in a combined hypoxic and hot conditions induces further enhancement of endothelial function. Twelve healthy males cycled at a constant workload (50% of their maximal oxygen uptake under normoxic/thermoneutral conditions) for 30 min in four different environments: exercise under normoxic condition (NOR: fraction of inspiratory oxygen or FiO2 = 20.9%, 20°C), exercise under hypoxic condition (HYP: FiO2 = 14.5%, 20°C), exercise under hot condition (HOT: FiO2 = 20.9%, 30°C), and exercise under combined hypoxia and hot conditions (HH: FiO2 = 14.5%, 30°C). Before, during, and after exercise, cardiovascular variables (e.g., heart rate, blood flow, and shear rate), blood variables, and endothelial function evaluated by flow-mediated dilation (FMD) were assessed. Heart rates were significantly higher throughout the HH trial's experimental period than the other trials (p < 0.05). However, in the HH trial, brachial artery blood flow and shear rate did not differ from those in other trials after exercise. Plasma catecholamines (epinephrine, norepinephrine, and dopamine) elevations in response to exercise were significantly higher in the HH trial than in the other three trials (p < 0.05). No considerable differences were observed in FMD responses among trials before and after the exercise. In conclusion, aerobic exercise in a combined hot and hypoxic environment further activated sympathetic nervous activity but did not considerably enhance blood flow, shear rate, or endothelial function.

Application of a supporting catheter in surgery for forearm arteriovenous fistula construction.

This study explored the feasibility of a supporting catheter combined with modified end-to-side anastomosis in the operation of radio-cephalic arteriovenous fistula (RC-AVF) and evaluated the clinical application value of this technique. Sixty patients underwent RC-AVF operations in our hospital from January 2022 to June 2022. All the patients were treated with modified end-to-side AVF anastomosis and divided into the control group or the test group depending on whether a supporting catheter was applied. The clinical data of 60 cases were analysed retrospectively. Intraoperative related indices, the first time the fistula was used, the success rate of first puncture, the blood flow of first dialysis, the maturity condition of fistula, the size of anastomosis, the diameter of radial artery and drainage vein, the blood flow of brachial artery 8 weeks after operation and the incidence of complications within 6 months after operation were compared between the two groups. Compared with that in the control group, the time spent on the vascular anastomosis in the test group was significantly shortened (p<0.05). The blood flow of the first dialysis, the size of the anastomosis, the diameter of the drainage vein, the blood flow of the brachial artery 8 weeks after the operation and the incidence of complications within 6 months after operation were significantly different between the two groups (p<0.05). In the RC-AVF operation, using a supporting catheter can not only increase operation efficiency by reducing surgical injury and difficulty of vascular anastomosis, but also improve postoperative prognosis. RC-AVF is worth promoting in clinical practice.

Circulatory Effects of Peripheral Chemoreflex Inhibition During Exercise in Treated Hypertension

The sensitization of the peripheral (carotid) chemoreflex can cause a sympathetically mediated restraint of blood flow to the exercising muscles in some disease states (e.g., heart failure, COPD). Such impairments in nutritive blood flow have the potential to impair exercise tolerance and raise exercising blood pressure (BP). Increased peripheral chemoreflex sensitivity and pronounced exercise-induced surges in BP have been reported in hypertension. Herein, we tested the hypothesis that suppressing peripheral chemoreflex sensitivity improves skeletal muscle blood flow during exercise in hypertension. Fourteen patients with treated hypertension (age 69±11 years, systolic BP 136±12 mmHg, diastolic BP 80±11 mmHg; mean ± SD) performed a resting baseline (3 min), an isocapnic hypoxia rebreathing test and rhythmic handgrip exercise (3 min at 50% of maximal voluntary contraction, 1 s contraction and 2 s relaxation) with either intravenous 0.9% saline (control) or low-dose dopamine (2 mcg·kg−1·min−1) to inhibit the peripheral chemoreflex. BP (finger plethysmography), heart rate (HR; electrocardiogram) and ventilation (V̇E; heated pneumotachometer) were recorded throughout. Brachial artery blood flow was monitored (duplex Doppler ultrasound) at rest (1 min average) and during handgrip (15 s averages), and vascular conductance calculated as brachial blood flow/mean BP. Dopamine blunted the peak (last 15 s) increase in V̇E during isocapnic hypoxic rebreathing compared to saline infusion (Δ6±6 vs. Δ9±5 L·min−1, P=0.026), while also attenuating peak mean BP (Δ3±4 vs. Δ8±6 mmHg, P=0.007). Dopamine did not change resting mean BP (95±10 vs. 98±10 mmHg, P=0.155) and HR (68±7 vs. 66±8 beats·min−1, P=0.100). However, dopamine increased resting brachial blood flow (59±20 vs. 48±16 mL·min−1, P=0.030) and vascular conductance (0.565±0.246 vs. 0.483±0.160 mL·min−1·mmHg−1, P=0.039) and decreased resting V̇E (10.5±3.2 vs. 11.5±3.1 L·min−1, P=0.036) versus saline. Handgrip increased brachial artery blood flow (p&lt;0.05 vs. rest after 45 s), vascular conductance (p&lt;0.05 vs. rest after 45 s) in both saline and dopamine trials, while mean BP, HR and V̇E were unchanged (main effect of time P=0.829, P=0.954 and P=0.255, respectively). Notably, brachial artery blood flow (e.g., Δ76±54 vs. Δ60±43 mL·min−1 at 60 s) and vascular conductance (e.g., Δ0.730±0.440 vs. Δ0.570±0.424 mL·min−1·mmHg−1 at 60 s) responses to handgrip were greater with dopamine than saline (main effect of condition both p&lt;0.0001). Collectively, these findings indicate that the use of low-dose dopamine to suppress peripheral chemoreflex sensitivity improves skeletal muscle blood flow during rhythmic handgrip exercise in patients with treated hypertension. Funding support provided by the Health Research Council of New Zealand (19/687) and the Sidney Taylor Trust. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Effect of 0.1 Hz Blood Flow Oscillations on Microvascular Blood Flow Responses Following Severe Ischemia

Background: We have shown that inducing 10 second (0.1 Hz) oscillations in arterial pressure and blood flow protects against reductions in tissue oxygenation during ischemia, independent of changes in macrovascular blood flow. However, it is unknown whether 0.1 Hz hemodynamic oscillations impacts microvascular function and vasodilatory capacity following severe ischemia. To examine this question, we assessed the reactive hyperemic response following a prolonged peripheral limb ischemia protocol with and without induced 0.1 Hz hemodynamic oscillations. Hypothesis: 0.1 Hz oscillations in blood pressure and blood flow will increase microvascular blood flow, assessed via reactive hyperemia following a 10-min period of ischemia. Methods: Thirteen healthy human participants (6M, 7F; 27.3 ± 4.2 y) completed two experimental protocols separated by ≥48 h. In both conditions, ischemia of the forearm was induced with a pneumatic cuff on the upper arm to decrease brachial artery blood velocity by ~70-80% from baseline. In the oscillation condition (OSC), 0.1 Hz oscillations in mean arterial pressure (MAP) and brachial artery blood flow were induced by inflating and deflating bilateral thigh cuffs every 5-s (10-s cycles; 0.1 Hz) throughout the forearm ischemia period. In the control condition (CON), the thigh cuffs were in place, but were inactive throughout the forearm ischemia period. Beat to beat arterial pressure was measured via finger photo plethysmography, and brachial artery diameter and blood velocity were measured via duplex Doppler ultrasound during baseline, ischemia, and the reperfusion period. The maximum mean brachial artery blood velocity, and 3-min area under the curve (AUC) of mean brachial artery blood velocity were used to determine the reactive hyperemia response. Results: The magnitude of forearm ischemia, indexed by the reduction in brachial artery conductance, was matched between conditions (CON: -74.8 ± 10.4% vs. OSC: -75.6 ± 6.7%, p=0.39). Reactive hyperemia was not different between conditions as indexed by maximum mean brachial artery blood velocity (CON: 36.4 ± 12.4 cm/s vs. OSC: 39.3 ± 11.2 cm/s, p=0.53) or 3-min brachial artery blood velocity AUC (CON: 1495 ± 744 (cm/s)2 vs. OSC: 1596 ± 804 (cm/s)2, p=0.74). Conclusion: Inducing 0.1 Hz hemodynamic oscillations during severe ischemia does not affect microvascular function, indexed by reactive hyperemia following release of the ischemic stimulus. A more direct measure of microvascular blood flow is needed to examine whether 0.1 Hz hemodynamic oscillations improves microvascular perfusion during ischemia. NIH Neurobiology of Aging &amp; Alzheimer’s Disease Training Grant (T32 AG02049; KAD); American Heart Association Transformational Project Award (19TPA34910743; CAR); American Heart Association Predoctoral Fellowship (23PRE1018469; KAD); UNTHSC Physiology and Anatomy Seed Grant 2021 (CAR). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Limb Position Influences Peripheral Arterial Stiffness Reduction with Reactive Hyperemia

Reactive hyperemia can acutely reduce peripheral arterial stiffness. The reduction in peripheral arterial stiffness with reactive hyperemia has been suggested to be flow dependent. However, no previous studies have manipulated the magnitude of hyperemia. We manipulated blood flow by altering limb position to test the hypothesis that a larger increase in blood flow would lead to a greater reduction in peripheral arterial stiffness. Fourteen healthy young adults (5 women; age: 25 ± 5 years; mean ± SD) were included in this study. Peripheral arterial stiffness assessed via brachial to radial pulse wave velocity (PWV) was measured by placing pulse tonometers simultaneously over the brachial and radial arteries. Doppler ultrasound was used to measure brachial arterial blood flow. Arterial blood pressure was continuously monitored via photoplethysmography on the middle finger of the contralateral hand. Reactive hyperemia was performed with the right arm positioned below (≍50°) and above (≍50°) heart level using a rapid-release cuff positioned on the upper arm, inflated to 220 mmHg, sustained for 5 min, then released. Measurements were recorded before cuff inflation and at 5, 15, and 30 min after cuff release. Repeated measures ANOVA revealed a significant condition effect (p&lt;0.01) with peripheral PWV higher with the arm below the heart. There was a significant time x condition interaction (p&lt;.05). At 5-min after reactive hyperemia, peripheral PWV was reduced more with the arm below the heart (9.58 ±1.65 to 7.26 ± 1.51 m/sec) than above the heart (7.08 ± 1.79 to 5.88 ± 1.43 m/sec). Mean arterial pressure did not change across time points (p&gt;0.05). Peak brachial artery blood flow was greater with the arm below the heart (477.37 ± 145 vs 368.64 ± 137 ml/min; p&lt;.001). The results show that reactive hyperemia produces an acute reduction in brachial to radial PWV. The reduction in peripheral arterial stiffness was greater when the arm was below the heart. The mechanism for position-related differences in the reduction in peripheral arterial stiffness with reactive hyperemia may be associated with the magnitude of increase in blood flow. REJ was supported by National Heart, Lung, and Blood Institute (5T32HL134634-04). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Influence of Resting Retrograde Shear Rate on Endothelial Function as Assessed by Flow Mediated Dilation

Shear stress profiles are an important determinant of endothelial function. Unidirectional blood flow enhances mean shear and protects endothelial function, whereas increased retrograde and oscillatory shear favors a proatherogenic environment. In this regard, acutely increasing retrograde shear has been shown to impair endothelial function. Also, previous studies have reported an elevation in retrograde shear in older adults that has been suggested to contribute to impaired endothelial function with age. However, the impact of having elevated retrograde shear at rest on endothelial function remains unclear. Therefore, we aimed to assess the associations between resting shear patterns and endothelial function, as measured by flow-mediated dilation (FMD) in a cohort of young and older adults. We hypothesized that higher retrograde shear rate and oscillatory shear index at rest would be related to a lower FMD value. Method: A total of 60 participants, 30 young adults (24 ± 5 years) and 30 older adults (62 ± 9 years), were studied. Resting brachial artery blood flow was measured using duplex Doppler ultrasound and retrograde shear rate and oscillatory shear index were calculated. Brachial artery FMD was used as a measure of endothelial function. Pearson correlations were used to investigate the associations between FMD, resting shear patterns, and age. Result: FMD was significantly lower in older compared to young adults (4.9 ± 2.7% vs. 7.6 ± 3.2%, p &lt; 0.01). Both retrograde shear rate and oscillatory shear index tended to be greater in older adults (-20.7 ± 15.1 s−1 vs. -15.2 ± 17 s−1, p = 0.062, and 10.7 ± 8% vs. 7.9 ± 8.0%, p = 0.056, respectively). FMD was not correlated with retrograde shear rate (r = -0.18, p = 0.17), or oscillatory shear index (r = -0.21, p = 0.11) in the entire cohort or in the young and older group alone. However, FMD, retrograde shear rate, and oscillatory index were moderately correlated with age: FMD (r = -0.45, p &lt; 0.01), retrograde shear rate (r = -0.32, p = 0.012), and oscillatory shear index (r = 0.33, p &lt; 0.01). Conclusion: These preliminary results suggest that resting retrograde shear and oscillatory shear index are not associated with reduced endothelial function in a cohort of young and old adults. Nevertheless, age-associated reductions in endothelial function and elevated retrograde shear were observed. This project was supported by the College of Nursing and Health Innovation. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Lower limb blood flow occlusion increases systemic pressor response without increasing brachial arterial blood flow redistribution in women.

This study was conducted to investigate the systemic hemodynamic and vascular changes in women during and after two commonly used clinical blood flow restriction (BFR) pressures at rest. There are minimal data regarding the independent effects of BFR on hemodynamic and systemic vascular changes due to pressor response, particularly among women. Therefore, this study investigated BFR-induced alterations in pressor response and systemic flow redistribution at rest during two commonly used pressures (50% and 80% limb occlusion pressure [LOP]). Fifteen women (22.1 ± 4.2 years) completed two randomised sessions involving 8-min of bilateral, lower limb restriction at 50% or 80% LOP followed by 8-min of recovery post-deflation. Changes in vascular (arterial diameter [DIA], time-averaged mean velocity [TAMV], volume flow [VF], and area) and hemodynamic (heart rate [HR] and blood pressure) measures over time (pre-, during, post-occlusion) and by session (50% vs. 80% LOP) were tested using repeated measures analysis of variance. Repeated measures correlations (rrm) quantified common intraindividual associations between BFR-induced hemodynamic and vascular responses. HR increased from baseline during 50% LOP and remained elevated during recovery (p < 0.05). HR increased from baseline during 80% LOP, while tibial VF and TAMV decreased (p < 0.03 for all). HR and TAMV values returned to baseline during recovery, while brachial artery VF decreased (p < 0.05). Changes in HR, brachial VF, and brachial TAMV were similar between 50% and 80% LOP (rrm = 0.32-0.70, p < 0.05 for all). At 80% LOP, changes in HR were positively correlated with brachial VF (rrm = 0.38) and TAMV (rrm = 0.43) and negatively correlated with tibial VF (rrm = -0.36) and TAMV (rrm = -0.30) (p < 0.05 for all). Results suggest that BFR at 80% LOP elicits an acute systemic pressor reflex without concomitant increases in brachial arterial flow, while 50% LOP elicits a subdued response.

Acute inspiratory resistance training enhances endothelium-dependent dilation and retrograde shear rate in healthy young adults.

Inspiratory resistance training (IRT) yields significant reductions in resting blood pressure and improves vascular endothelial function. Our objective was to quantify the acute effects of IRT on brachial artery flow-mediated dilation (FMD) and shear rates (SRs) in healthy men and women. Twenty young adults (22.9 ± 3.4 years; 10 male, 10 female) completed a single bout of IRT or Rest condition in a randomized crossover design. Brachial artery FMD was performed before, 10 min after, and 40 min after the assigned condition. Brachial artery blood flow velocities were collected during IRT, separated by breathing cycle phase, and converted into SRs. FMD improved 10 min post-IRT (+1.86 ± 0.61%; p = 0.025) but returned to baseline by 40 min post-IRT (p = 0.002). Anterograde SR decreased by 10% and retrograde SR increased 102% during resisted inspiration, relative to baseline SR (p < 0.001). Anterograde SR increased by 7% in men and women (p < 0.001) and retrograde SR decreased by 12% in women but not men (p = 0.022) during unresisted expiration, relative to baseline SR. A single bout of IRT elicits a transient enhancement in FMD in both men and women. Acute IRT-related enhancements in SRs may contribute to sustained improvements in FMD that have been reported previously.

Sex-specific microvascular and hemodynamic responses to passive limb heating in young adults.

We examined sex-specific microvascular reactivity and hemodynamic responses under conditions of augmented resting blood flow induced by passive heating compared to normal blood flow. Thirty-eight adults (19 females) completed a vascular occlusion test (VOT) on two occasions preceded by rest with or without passive heating in a randomized, counterbalanced order. Skeletal muscle tissue oxygenation (StO2, %) was assessed with near-infrared spectroscopy (NIRS), and the rate of desaturation and resaturation as well as maximal StO2 (StO2max) and prolonged hypersaturation (area under the curve, StO2AUC) were quantified. Before the VOT, brachial artery blood flow (BABF), vascular conductance, and relative BABF (BABF normalized to forearm lean mass) were determined. Sex × condition ANOVAs were used. A p-value ≤.05 was considered statistically significant. Twenty minutes of heating increased BABF compared to the control (102.9 ± 28.3 vs. 36.0 ± 20.9 mL min-1; p < .01). Males demonstrated greater BABF than females (91.9 ± 34.0 vs. 47.0 ± 19.1 mL min-1; p < .01). There was no sex difference in normalized BABF. There were no significant interactions for NIRS-VOT outcomes, but heat did increase the rate of desaturation (-0.140 ± 0.02 vs. -0.119 ± 0.03% s-1; p < .01), whereas regardless of condition, males exhibited greater rates of resaturation and StO2max than females. These results suggest that blood flow is not the primary factor causing sex differences in NIRS-VOT outcomes.

The vascular response to acute sauna heating is similar in young and middle-aged adults.

Sauna has been linked to a reduction of cardiovascular disease risk and is a promising nonpharmacological treatment for populations at risk of cardiovascular disease. This study examined the vascular response to an acute bout of sauna heating in young and middle-aged individuals. Ten young (25 ± 4 yr, 6 males and 4 females) and eight middle-aged adults (56 ± 4 yr, 4 males and 4 females) underwent 40 min of sauna exposure at 80°C. Esophageal and intramuscular temperatures, brachial and superficial femoral artery blood flow, artery diameter, and shear rates were recorded at baseline and following heat exposure. Brachial artery flow-mediated dilation (FMD) was measured at baseline and following 90 min of recovery. Esophageal and muscle temperatures increased similarly in the young and middle-aged adults by 1.5 ± 0.53 and 1.95 ± 0.70°C, respectively (P < 0.05). The shear rate increased by 170-200% (P < 0.001), while blood flow increased by 180-390% (P < 0.001) in the superficial femoral and brachial arteries, respectively, and did not differ between age groups (P = 0.190-0.899). Systolic blood pressure was reduced from 135 ± 17 to 122 ± 20 mmHg (P = 0.017) in middle-aged participants. These data indicate that young and middle-aged adults have similar vascular responses to acute sauna heating.NEW & NOTEWORTHY Sauna therapy has been shown to improve cardiovascular health and function in older adults and individuals with cardiovascular disease risk factors. Specifically, improvements in vascular function have been reported and have been attributed to the increased hemodynamic stimuli on the vasculature associated with thermal stress. The present study quantified this hemodynamic response to a sauna protocol associated with improved cardiovascular health across the lifespan. Our data show that middle-aged adults have the same shear rate and blood flow response to sauna as young adults.

Jaboticaba berry (Myrciaria jaboticaba) supplementation protects against micro- and macrovascular dysfunction induced by eccentric exercise: a randomized clinical trial.

Physical activities that are unaccustomed and involve eccentric muscle contractions have been demonstrated to temporarily impair macrovascular and microvascular functions, which may be caused by exercise-induced oxidative stress. Jaboticaba (Myrciaria jaboticaba) is a famous Brazilian berry that has been described to exhibit high antioxidant activity. However, no human study has investigated the protective effects of jaboticaba consumption against the vascular damage induced by eccentric exercise. Therefore, the present study aimed to assess whether supplementation with jaboticaba berry juice could positively affect macro- and microvascular functions within 48 hours after eccentric exercise. This randomized, double-blind, placebo-controlled, parallel trial enrolled 24 healthy participants consuming 250 mL per day of jaboticaba berry juice (containing ∼1,300 mg of total polyphenols) or placebo for 6 days. At the baseline, pre-exercise, and 24 h and 48 h postexercise stages, blood samples were taken for analysis of reduced glutathione (GSH) levels. Also, brachial artery flow-mediated dilation (FMD), blood flow, and tissue oxygen saturation (StO2) responses to 5-minute cuff occlusion were assessed using Doppler ultrasound and near-infrared spectroscopy, respectively. Our findings revealed significant decreases in blood GSH (P < 0.001, ES = 0.76), FMD (P = 0.005, ES = 0.48), reperfusion slope of StO2 (P = 0.018, ES = 0.42) at 24 h and blood flow (P = 0.012, ES = 0.42) at 48 h following eccentric exercise in the control group as compared to the jaboticaba berry juice group. Our results demonstrated that jaboticaba berry juice prevented the exercise-induced increase in reactive oxygen species production and protected macro- and microvascular functions against the damage caused by eccentric exercise, suggesting that jaboticaba berry consumption could protect the vascular function under conditions of imbalance in redox homeostasis.

A Case of Upper Limb Amputation Managed with USG-guided Continuous Infraclavicular Nerve Block for Improved Postoperative Analgesia

Phantom Limb Pain (PLP) is defined as any perceived painful sensation localised to the region of the amputated body part, while phantom limb sensations are non painful sensations emanating from the phantom limb, including proprioceptive awareness, kinetic, exteroceptive, and superadded sensations. The mode of anaesthesia administered during amputation is an important factor in determining the emergence of PLP or phantom sensations. The majority of patients requiring emergency care are victims of traumatic injuries to the upper limbs, which are most often treated conservatively. The authors present the case of a 67-yearold male patient who sustained a fall on his arm while carrying a metal container, resulting in a laceration to his left arm that led to disruption of brachial artery blood flow, necessitating amputation. Although upper limb injuries are relatively common, concurrent vascular injuries are rare. However, when a major vessel such as the brachial artery is injured, amputation may be required. This loss of a limb can result in PLP. To prevent this, the authors used a unique and rare protocol of Continuous Peripheral Nerve Block (CPNB) in the present case. It not only underscored the importance of intraoperative analgesia in preventing PLP but also proved to be a crucial anaesthetic tool in facilitating the surgery and providing the patient with a more comfortable postoperative recovery.

Heating the scanning environment during ultrasound upper limb mapping: Impact on arteriovenous fistula creation outcomes and sonographer's perceptions of heating method useability

AbstractAimThis study explores the impact on arteriovenous fistula (AVF) creation and maturation of four methods of heating the scanning environment during ultrasound upper limb mapping, and sonographer perceived useability of the environments.MethodA retrospective audit at Orange and Bathurst hospitals involving patients who underwent ultrasound upper limb mapping (2016–2022). Patients were scanned using warm gel and three additional methods of warming. Two sonographers provided their preference and opinions on each environment. Data on AVF type, brachial artery blood flow (QBRA), AVF maturity status at 3 and 6 months and intervention within this timeframe was retrieved. Data from the three additional heated environments was combined for analysis (heated environments) against the heated gel only environment (gel environment).ResultsEighty‐five patients met selection criteria. There was no significant difference in the proportion of successfully created AVFs between the heated and the gel environments (90% vs. 94%). A greater percentage of AVFs mapped in the heated environments reached maturity without intervention compared to the gel environment (70% vs. 48%, respectively). There was a statistically significant higher QBRA in the AVFs mapped in the heated environments (1.25 L/min) that reached maturity by 3 months without intervention compared to the gel environment (0.95 L/m; p = .008). Sonographers found a warm blanket/electric throw the easiest methods of heating the scanning environment.ConclusionUsing an electric throw and/or a warm blanket during ultrasound upper limb mapping is practical and optimises the scan environment, which provides surgeons with quality information that ultimately improves AVF creation outcomes.

Reduction in peripheral arterial stiffness after reactive hyperemia is dependent on increases in blood flow.

The acute reduction in peripheral arterial stiffness during reactive hyperemia is assumed to be flow-mediated; however, the mechanism remains unproven. We hypothesized that restricting the blood flow increase during reactive hyperemia would abolish the reduction in peripheral arterial stiffness. Fourteen healthy young adults (5 females, 25 ± 5 years, mean ± SD) underwent reactive hyperemia with a rapid-release cuff on the upper arm inflated to 220 mmHg for 5 min: once with unrestricted blood flow and once with restricted blood flow by manually applying pressure to the brachial artery. Brachial-radial pulse wave velocity (PWV) was measured with tonometers over brachial and radial arteries before cuff inflation and at 5, 15, and 30 min after release. Brachial blood flow was monitored with Doppler ultrasound. Baseline brachial-radial PWV was similar between conditions (10.3 ± 1.8 vs. 10.7 ± 1.7 m/s). With unrestricted flow, PWV decreased 5 min post-reactive hyperemia (8.6 ± 1.1 m/s; p < 0.05) and returned near baseline at 15 and 30 min post (p < 0.05). With restricted flow, PWV did not change (p > 0.05) post-reactive hyperemia. Reactive hyperemia acutely reduced peripheral arterial stiffness, but not when brachial artery blood flow increase was restricted. This suggests that the reduction in peripheral arterial stiffness during reactive hyperemia depends on increased blood flow.

Effect of preoperative arterial diameter on hospitalization and mortality in patients undergoing hemodialysis with forearm arteriovenous fistula access.

As pointed out by the recent Kidney Disease Outcomes Quality Initiative Clinical Practice Guideline for Vascular Access, the current quality of evidence supporting preoperative vascular anatomy and patient outcomes is suboptimal and insufficient to make recommendations. This study assessed arteriovenous fistulas (AVFs) created with different preoperative arterial diameters on hospitalization and mortality rates in patients undergoing hemodialysis at the authors' center. Data from 261 patients who underwent HD between 2017 and 2019 were retrospectively examined. Differences in mortality and hospitalization rates between patients with different preoperative arterial diameters were compared, and risk factors for mortality and hospitalization were analyzed. Smaller preoperative artery diameter (<2 mm) was associated with all-cause mortality (risk ratio [RR] 1.61 [95% confidence interval (CI) 1.45-1.90]; p < 0.01), and access-related (RR 1.68 [95% CI 1.24-2.44]; p < 0.01), and congestive heart failure (CHF)-related (RR 0.67 [95% CI 0.38-1.01]; p = 0.04) hospitalization. Longer catheter-dependent duration (⩾60 days) was associated with access-related hospitalization (RR 1.48 [95% CI 1.07-2.11]; p = 0.03), and higher postoperative brachial artery blood flow (⩾1500 mL/min) was associated with CHF-related hospitalization (RR 1.58 [95% CI 1.02-2.29]; p < 0.01). Higher postoperative brachial artery blood flow (⩾1500 mL/min) was associated with all-cause mortality (hazard ratio [HR] 1.20 [95% CI 1.09-2.32]; p = 0.04), whereas preoperative artery diameter (HR 0.98 [95% CI 0.93-1.86]; p = 0.08) and catheter-dependent duration (HR 1.06 [95% CI 0.47-2.13]; p = 0.82) were not associated with all-cause mortality. In this cohort, smaller preoperative artery diameter was associated with all-cause and access-related hospitalizations, while a larger preoperative artery and higher postoperative brachial blood flow were associated with CHF-related hospitalization. However, only higher postoperative brachial blood flow was associated with all-cause mortality.

Sex differences in muscle contraction-induced limb blood flow limitations.

To determined sex differences in absolute- and %-reductions in blood flow during intermittent muscular contractions as well as relationships between blood flow reductions and time to task failure (TTF). Thirteen males (25 ± 4 years) and 13 females (22 ± 5 years) completed intermittent isometric trapezoidal forearm flexion at 50% maximal voluntary contraction until task failure. Doppler ultrasound was used to measure brachial artery blood flow (BABF) during the 12-s plateau phase and 12-s relaxation phase. Target torque was less in females than males (24 ± 5 vs. 42 ± 7 Nm; p < 0.001); however, TTF was not different between sexes (F: 425 ± 187 vs. M: 401 ± 158s; p = 0.72). Relaxation-phase BABF at end-exercise was less in females than males (435 ± 161 vs. 937 ± 281mL/min; p < 0.001) but contraction-phase BABF was not different (127 ± 46 vs. 190 ± 99mL/min; p = 0.42). Absolute- and %-reductions in BABF by contraction were less in females than males (309 ± 146 vs. 747 ± 210mL/min and 69 ± 10 vs. 80% ± 6%, respectively; both p < 0.01) and were associated with target torque independent of sex (r = 0.78 and 0.56, respectively; both p < 0.01). Absolute BABF reduction per target torque (mL/min/Nm) and TTF were positively associated in males (r = 0.60; p = 0.031) but negatively associated in females (r = -0.61; p = 0.029). This study provides evidence that females incur less proportional reduction in limb blood flow from muscular contraction than males at a matched relative intensity suggesting females may maintain higher levels of muscle oxygen delivery and metabolite removal than males across the contraction-relaxation cycle of intermittent exercise.

Effect of far-infrared therapy device on arteriovenous fistula maturation and lifespan in hemodialysis patients: a randomized controlled clinical trial.

Arteriovenous fistula (AVF) is the first choice of vascular access for hemodialysis treatment, and its surgical maturity rate is not high, and its postoperative complications (mostly stenosis) significantly shorten its life. At present, there are few studies on treatment methods to improve the maturity and survival of AVF. In this study, the effect of far infrared therapy (FIR) on the maturity and longevity of arteriovenous fistula in hemodialysis patients was discussed, and the protective mechanism of AVF induced by FIR therapy was explored, aiming at exploring a new treatment method. The hemodialysis patients admitted to the 900th Hospital of the Chinese Joint Logistics Support Force of the People's Liberation Army from January 2021 to April 2023 were randomly divided into control group and intervention group, with 40 cases in each group. Among them, the control group was coated with mucopolysaccharide polysulfonate cream; Intervention group: The patients were treated with mucopolysaccharide polysulfonate cream and far infrared radiation at the same time. After 3 months' intervention, the arteriovenous fistula (vein diameter, mature time of arteriovenous fistula, blood flow controlled by pump during dialysis, blood flow of brachial artery during dialysis and the occurrence of complications of internal fistula (oozing, occlusion and infection) and the pain score (numerical rating scale, NRS) of the two groups were compared, and the curative effects were compared. There was no significant difference in general data between the two groups (P > 0.05), which indicated that the study was comparable. After 3 months' intervention, the vein diameter, pump-controlled blood flow and brachial artery blood flow in the intervention group were significantly higher than those in the control group (P < 0.05). And the maturity time, NRS score and complication rate of arteriovenous fistula were significantly lower than those of the control group (P < 0.05). The primary patency rate of AVF in the intervention group was higher than that in the control group, and the overall patency rate between the two groups was statistically significant (P < 0.05). As a promising new treatment method, far infrared therapy can effectively promote the maturity of AVF, increase venous diameter, pump controlled blood flow during dialysis, brachial artery blood flow during dialysis, and prolong the service life of AVF.